The present invention relates to devices for dispensing chemicals from an aerosol container in an automated manner. More particularly it provides dispensers which adjust the length of their automated dispensing cycles to correct for can pressure differentials resulting from the can being used in more and more emptied states.
Various devices have been developed where chemicals of interest (e.g. cleaning formulations; air treatment formulations) are dispensed from an aerosol container. For example, in U.S. Pat. No. 6,820,821 an automated shower enclosure cleaner dispenser was hung from a shower head. By pushing a button on the dispenser a controller caused shower cleaner to be automatically sprayed from the unit, for a set period. The cleaner could be stored in an aerosol container.
As another example, in U.S. patent application publication 2009/0236362 a dispenser was disclosed for dispensing air care product (e.g. insect repellent; fragrance) from an aerosol can, in an automated manner.
Note further that in U.S. Pat. No. 7,603,726 there was disclosed a toilet bowl cleaner dispenser. A spray nozzle was mounted over the rim of a toilet bowl, the nozzle being fed toilet bowl cleaner from an aerosol can whose spraying was triggered by a foot pedal.
A common feature of these and other analogous prior art systems is that they did not take into account pressure differences in the aerosol can that resulted as the chemical was being used. For instance, an automated ten second spray cycle when the aerosol can was completely filled could deliver more product than a ten second spray cycle when the can was three-quarters empty. This could result in too little product being delivered for some applications (when. the can was near empty) if the system was set based on expected delivery volume upon can initiation. Alternatively, if one set up the timing to insure adequate delivery when the can was near empty, chemical would be wasted when the can was newly installed.
In U.S. patent application publication 2003/0056587 a thermochromatic system was disclosed for indicating how much chemical was left in an aerosol can as it was being used. However, that information was not used to alter the length of the spray cycle as the can emptied.
Hence, a need still exists for improved automated aerosol dispensing systems.